With the development of Internet and the popularity of big-screen multi-function UEs, a lot of mobile data multimedia services and various high-bandwidth multimedia services have emerged, such as video conference, television broadcast, video on demand, advertisement, online education, interactive game and the like; these services not only meet the requirement of a mobile user on multiple services, but also bring a new business growth to a mobile operator. These mobile data multimedia services require that multiple users can receive the same data simultaneously, and have advantages of large data amount, long duration; delay sensitivity and the like compared with a general data service.
In order to utilize a mobile network resource effectively, the 3rd Generation Partnership Project (3GPP) proposes an MBMS service which is a technology for transmitting data from one data source to a plurality of target UEs; and this technology realizes sharing of network resources (including a core network and an access network) and improves the utilization rate of the network resource (particularly an air interface resource). The MBMS service defined by the 3GPP not only can realize multicast and broadcast of messages of low-rate plain texts, but also can realize multicast and broadcast of high-rate multimedia services and provide a variety of videos, audios and multimedia services. The MBMS service undoubtedly follows the trend of the future development of mobile data and provides a better business prospect for the development of 3G.
In a Long Term Evolution (LTE) system, a UE may have two operating modes: a Radio Resource Control (RRC) Idle mode or an RRC Connected mode. A mobility of a UE in the idle mode is implemented by a cell selection or cell reselection, and the process of the cell selection or cell reselection is initiated by the UE: the cell reselection first considers a priority of a frequency, wherein the priority of the frequency is provided by a system message; the UE preferentially selects a frequency with a top priority to perform a cell reselection; and the mobility of a UE in the connected mode is implemented by a handover, wherein the handover process is initiated by an evolved NodeB (eNB) in which a source cell is located.
The characteristics of the MBMS service lie in large data amount, long duration of a UE receiving a service and constant average data rate. These characteristics determine that configurations of scheduling and control signaling of these MBMS services are semi-static, that is, scheduling information and control signaling information of the MBMS service keep unchanged for a long time, wherein the information mentioned here is periodically sent by an MBMS Control Channel (MCCH) and thus is called MCCH information. An evolved MBMS (eMBMS) system might have a plurality of MCCHs, wherein each MCCH corresponds to a different Multicast Broadcast Single Frequency Network (MBSFN) and only bears the control signaling information of the MBMS service sent by a corresponding MBSFN. The configuration information of the MCCH is indicated through a System Information Block (SIB) 13 and the scheduling of the SIB13 is indicated through an SIB1.
The MBMS technology is introduced in a Release 9 (R9) of the LTE system and is enhanced in a Release 10 (R10). In the R9, control signaling and user data of the MBMS service are separately transmitted and are respectively called a Control Plane (CP) and a User Plane (UP). The CP controls the sending of the UP data by controlling start, update and end of a service, so as to implement the sending of the basic MBMS service. In the R100, in order to improve the resource utilization rate of an MBMS system and to facilitate the management of an operator, the MBMS technology is enhanced, mainly including: a counting mechanism and a priority based preemption mechanism.
An LTE Advanced (LTE-A) system introduces a Carrier Aggregation (CA) technology, that is, multiple carriers with different frequencies (bands) which can be continuous or discrete are stored at one location and a network side sends data to a UE using two or more carriers simultaneously. A UE in the connected mode with the CA capability can receive data on two or more carriers simultaneously. Each UE at least supports the aggregation of two Component Carriers (CCs); the network side allocates and indicates to a UE a Primary Cell (Pcell) of the UE and a Secondary Cell (Scell) of the UE. A UE in an idle state hosts in its own Pcell. A UE only receives broadcast system information and a paging message in the Pcell, and does not retrieve a public retrieval region of a Physical Downlink Control Channel (PDCCH) in the Scell.
The MBMS system defines an MBMS service area, an MBSFN area and a reserved cell of the MBSFN area, wherein the MBMS service area refers to an area sending specific MBMS session data: the MBSFN area refers to an area formed by a plurality of cells which collaborate to finish a MBSFN transmission; a reserved cell of the MBSFN area refers to a cell sending other services with a limited power on a corresponding MBSFN sub-frame resource and not participating in the MBSFN transmission in the MBSFN area. In this application, all cells other than the reserved cell in the MBSFN area are called non-reserved cells. The MBMS service area is dynamically configured by a Broadcast-Multicast Service Center (BM-SC) according to a service requirement; the MBSFN area is statically or semi-statically configured by a Multi-cell/multicast Coordination Entity (MCE); and the reserved cell is configured by the MCE. Generally, the MBMS area is greater than the MBSFN area, as shown in FIG. 1.
The MBMS service is provided by the BM-SC. The BM-SC sends MBMS session data to a network element in the MBMS service area, wherein the network element includes an MBMS Gateway (MBMS-GW) and a Packet Data Network Gateway (PDN-GW). The MBMS-GW sends the MBMS session data to an eNB joining a multicast group in a multicast manner, and the eNB located in the same MBSFN area sends the MBMS session data to a UE in the MBSFN area in an MBSFN manner, which is called a Point To Multipoint (PTM) transmission or MBSFN transmission. After the PDN-GW receives the MBMS session data, if a Unicast service bearer is established, the PDN-GW sends the MBMS session data to a Serving Gateway (S-GW) and the S-GW sends the MBMS session data to an eNB which then sends the MBMS session data to a corresponding UE, which is called a Point To Point (PTP) transmission. The transmission process above indicates that: in the MBMS service area, the UE can receive the MBMS service through a PTP or PTM mode. For the PTP mode, generally the UE initiates a Packet-switched Stream (PSS) client request to a PSS server.
Before the MBMS service session starts, the BM-SC first performs a service announcement; the purpose of the announcement is to send a brief introduction of the MBMS service to the UE, wherein the announcement can be sent by the following ways: an MBMS bearer; or, an interaction mode, for example, Hyper Text Transport Protocol (HTTP); or, a PTP push mode, for example, Short Message Service (SMS), Multimedia Message Service (MMS), HTTP push and the like.
During the study and practice process of the present technology, it is found that the present technology has problems as follows: when a UE that is receiving the MBMS service is moving, only the service continuity of a Unicast service is considered during the decision of a cell reselection by the UE or a handover by a network side; if a plurality of CCs is deployed in the network, the UE probably performs a cell reselection or cell handover to a target cell of which the CC is different from that of the MBMS service, thus the MBMS service is interrupted and the MBMS service experience of users is reduced; in the MBMS service area, when the UE that receives the MBMS service through the PTM mode moves to a non-MBSFN area or a reserved cell in the MBSFN area, the MBMS service is interrupted, thus the MBMS service experience of users is reduced; in the MBMS service area, when the UE that receives the MBMS service through the PTP mode moves to a non-reserved cell in the MBSFN area, the MBMS service is sent through the PTP mode and the PTM mode simultaneously, thus waste of resources is caused.